PHOTOINDUCED RECHARGING PROCESSES OF NIGA IN GAP AND PARAMAGNETIC-RESONANCE OF NIGA(2+)

LEC-grown GaP:Ni in which the Fermi level is pinned by either the Ni2+/Ni3+ or Ni+/Ni2+ level has been investigated by optical absorption (OA), thermally detected (TD) optical absorption, electron paramagnetic resonance (EPR) and TD.EPR. The spectroscopic features, subsequently assigned to Ni(Ga)+, Ni(Ga)2+ and Ni(Ga)3+, were monitored under external illumination. The analysis of their spectral dependence together with the angular variation of a set of new TD.EPR peaks strongly suggests that the latter results are due to Ni(Ga)2+ ions. It also provides identification of the photoinduced recharging processes involving the three charge states of isolated Ni(Ga). An orthorhombic Jahn-Teller model is presented to describe the Ni(Ga)2+ resonances in the TD-EPR experiments.